According to an ultrasonic diagnostic apparatus, the ultrasonic reflectance of a biomedical tissue at a diagnosis site in a body being examined is measured by ultrasonic waves and the reflectance is converted to brightness to thereby display the measurement result as a reflectance tomographic image (hereinafter abbreviated as “tomographic image”) of the diagnosis site.
Furthermore, according to the ultrasonic diagnostic apparatus, it has been recently implemented that the displacement of a biomedical tissue is measured on a tomographic image which is acquired by applying a pressure variation to the biomedical tissue with a probe or the like, distortion or elastic modulus of the biomedical tissue is calculated from the spatial differentiation of the displacement concerned, or the distribution of distortion or elastic modulus in the biomedical tissue is displayed as an image (hereinafter referred to as “elastic image”). The elastic image is displayed by adding red, blue and other color information in accordance with the distortion or the elastic modulus of the biomedical tissue. By referring to this elastic image, a hard portion of the biomedical tissue is particularly made clear, and the expansion or size of tumor can be diagnosed (for example, Patent Document 1).
In general, in order to perform high-precision diagnosis, it is preferable that the elastic image has high image quality. However, much time is needed to obtain an elastic image having high image quality, and thus much time is unavoidably taken if only an elastic image of high image quality is obtained.
For example, an conventional ultrasonic diagnostic apparatus having an elastic image diagnosing function disclosed in (Patent Document 1) has only one kind of elastic image acquisition mode which is suitable to close examination, and obtains an elastic image by only the acquisition mode having high image quality and a fixed frame rate (hereinafter referred to as “high-precision mode”).
However, the (Patent Document 1) pays no attention to such an acquisition mode for quickly acquiring an elastic image at a high frame rate that diagnosis can be performed in a short time (hereinafter referred to as screening mode).
Patent Document: JP-A-2005-118152